Bridge Repair Methods — U.S./Canadian Practice

Abstract

Nearly half of the highway bridges in the United States have been classified as structurally deficient or functionally obsolete. The question of functional obsolescence will not be dealt with. Reasons for the structural deficiencies are numerous, as a number of the bridges are over fifty years old and have not been properly maintained. Over a period of time, environmental corrosion has accumulated. In addition, increases in the number of trucks using the highways as well as the rise in allowable truck weights has led to increasing amounts of fatigue cracking. Many structures have welded details that have been identified as susceptible to fatigue cracking only after they were built. Rules used to design some structures often oversimplify member interactions and connection behavior, resulting in distortion-induced fatigue cracking in a large number of different types of bridge structures.

Due to the magnitude and breadth of the bridge deficiency problem, and the prohibitive costs of new construction, a large effort in the repair and rehabilitation of existing bridges is required. Careful examination of the causes of fatigue cracking and corrosion accumulation, coupled with effective technology transfer, will help to prevent the development of similar situations in future construction. This paper briefly reviews the causes of some of the fatigue cracking being experienced in bridge structures. Various repair and retrofit procedures are reviewed, and examples of typical applications of these procedures are examined. It also examines examples of severe corrosion and the inability to detect active corrosion cell activity.